The present invention relates to a light source apparatus, an optical modulation apparatus, a display apparatus, a light condense illumination apparatus and a projection type color display apparatus, capable of effectively performing light condense illumination relative to a predetermined range as well as attaining miniaturization and a thinner size.
A discharge lamp such as a high-pressure mercury lamp, a metal halide lamp or the like is utilized as a light source in a conventional projection type color display apparatus. Such a discharge lamp is large in size, and hence, a size of an optical system as a whole including a light source portion becomes large. In addition, because light emitted by the discharge lamp includes infrared light, a large amount of heat is radiated to an environment, which makes filters, a cooling fan and so on indispensable. Thus, there are many disadvantageous in the conventional projection type color display apparatus utilizing the discharge lamp in terms of cost, size, noise, etc.
In addition, the light radiated from the lamp mentioned above is white light. Accordingly, in order to perform color-displaying, it is required to separate the light into three colors of R (red light), G (green light) and B (blue light) as three primary colors of light, and to provide an optical modulator with respect to each of the colored lights. Each of the colored lights modulated by the corresponding one of the optical modulators is then synthesized, and the synthesized light is then directed toward a projection lens. Hence, a further problem arises in the conventional projection type color display apparatus in that the optical system thereof becomes even large in order for performing the color separation and the color synthesis.
As an alternative method in the conventional projection type color display apparatus described above, there has been known a method in which the modulation of light is performed by a single liquid crystal optical modulator provided with a color filter, without performing the color separation. However, since the number of pixels of the optical modulator is restricted, the number of pixels becomes approximately one-third, and thus such a method cannot perform high definition displaying.
On the other hand, there has been proposed recently a projection type color display apparatus in which light emitting diodes (LEDs) are utilized as a light source. Because the LED is small in itself, modulation speed is fast, and a so-called field sequential type displaying is thereby possible.
The field sequential type displaying is a type of displaying in which a single optical modulator is used, and the LEDs of respective three colors of R, G, B are time-sequentially lit and an optical modulation element is turned on or off in synchronization with the time-sequential lighting of the LEDs. This method enables performing of the color-displaying with the single optical modulator without decreasing the number of pixels. Therefore, luminous efficiency improves greatly, and accordingly, there has been a growing possibility that the LEDs, although brightness thereof used to be scarce, may be adopted for an illumination light source of a display apparatus. However, even if the improvement of the luminous efficiency is realized, consideration for even brighter display apparatus is desired.
As a conventional technology relating to a display apparatus such as a digital projector or the like, to an optical modulation apparatus used in such a display apparatus, and to a general illumination optical system such as an illumination apparatus, the inventions disclosed in JP2001-343706A, JP2002-244211A, JP2002-303932A and JP-H10-301201A are known. A technology relating to a general illumination optical system apparatus, in which a white light lamp such as a high-pressure mercury lamp, a xenon lamp, a metal halide lamp and so on is used as a light source, is disclosed on pages 606-614, “The Optical Efficiency of LCD Projector Systems” of a non-patent document titled “Optical and Electro-Optical Engineering Contact” vol. 37, published in 1999.
JP2001-343706A discloses the invention in which a plurality of light sources, each structured by LEDs and a coupling lens, are arranged, and each light emitted therefrom is adapted to illuminate a light valve through a condenser lens, integrator and two condenser lenses.
JP2002-244211A discloses the invention in which LEDs as a light source and an illumination system having a polarization converting element allay are employed. The invention of JP2002-244211A is possible to reduce a loss of light due to polarization and to achieve a balance between miniaturization and high luminous efficiency.
As to JP2002-303932A, it discloses the invention which provides a displaying method in a case in which a reflective type optical modulation element is used.
With regard to JP-H10-301201A, the invention thereof provides a projector apparatus in which LEDs are utilized as an illumination light source. The invention disclosed in JP-H10-301201A uses an alley light source which is larger than a liquid crystal spatial modulator and also uses a reduction optical instrument for an illumination system, so as to improve brightness.
However, the inventions described above have drawbacks as follows.
For example, the technology disclosed in the non-patent document is accompanied with a large amount of infrared ray, i.e. accompanied with radiation of a large amount of heat. It is also difficult to maintain a balance of a light amount of each R, G and B as so-called three primary colors of light by color-separation/synthesis performed by a dichroic mirror/prism, and thus there is a limitation in color-reproducibility. Further drawbacks are that a size of a body of the apparatus becomes large, and the number of components is increased.
The invention disclosed in JP2001-343706A, which uses the LEDs, LDs (Laser Diodes) or the like as a substitute for the conventional illumination light source, disposes the light sources, the lenses integral with the light sources, a microlens array, a condenser lens, two microlens arrays structuring the integrator, the condenser lens and the condenser lens, in this order. Accordingly, the number of components is large, and miniaturization is also restricted.
Furthermore, the projector apparatus in which the LEDs or the like are adopted as the illumination light source is provided according to the invention disclosed in JP-H10-301201A. The invention thereof utilizes the reduction optical instrument for the illumination system to improve the brightness. However, it is to be noted that an afocal system which has no focal point is shown therein for the reduction optical instrument. Accordingly, there may not be a problem when an incident light flux is parallel light, but because the actual LED light has a light distribution characteristic (divergence characteristic), it is difficult to effectively utilize non-parallel light.